Some presently known load-responsive linking devices for use with brake pressure regulators of vehicles may have a fulcrum lever which is pivotal about a fulcrum connected to the regulator housing and is subjected to the tensional influence of a primary spring which is connected thereto between the free end of the lever and the point of connection of the regulator housing and whose initial tension is variable under the tensional influence of a counteracting secondary spring according to the distance between the sprung vehicle body and the unsprung vehicle axle, said lever abutting against a piston rod elongation of the brake power regulator for operating the latter.
As is known, the purpose of a brake pressure regulator when used in the manner above set forth in connection with a load-responsive linking device of the above-mentioned type, is to increase brake pressure in proportion to increase of vehicle load and to decrease said brake pressure in proportion to decrease of vehicle load, in accordance with the initial tension of the primary spring as varied by the influence of the secondary spring according to the distance between the sprung vehicle body and the unsprung vehicle axle.
Presently known load-responsive linking devices of the type described above, in which the fulcrum lever of the brake pressure regulator is subjected to opposing forces of a primary spring anchored to the sprung vehicle body through the regulator piston, which is usually mounted on the vehicle body, and a secondary spring anchored to the unsprung vehicle axle, have the disadvantage that the axle oscillations which occur during operation of the vehicle and may be of considerable amplitude, are transmitted to the lever of the brake pressure regulator by way of the secondary spring, thus subjecting both springs to considerable alternating stresses, which especially in the event of a failure of the primary spring acting on the regulator piston via the fulcrum lever, would affect the safety of the vehicle, because the brake pressure to be obtained for effective braking could no longer be built up in the associated brake circuit, and which alternating stresses would further subject the linking points of the linking device and the parts of the brake pressure regulator to increased wear.